A data reading operation is a most common operation in the data processing field. Generally, a process of the data reading operation is: A data reading device sends a read operation instruction to a data storage unit, and after receiving the read operation instruction, the data storage unit obtains, according to an address carried in the read operation instruction, data corresponding to the address, and returns the data corresponding to the address to the data reading device. According to the foregoing process, the data reading device obtains the data corresponding to the address. However, during the process in which the data reading device performs the foregoing read operation, an attacker obtains the address carried in the read operation instruction and the data corresponding to the address by monitoring a data bus between the data and a controller of the data reading device, and can arbitrarily tamper with the data. Consequently, data is leaked, and data security is seriously threatened.